If EGT gauge mounted post turbo...

[OT-OF-HERE!!]

If the EGT gauge is mounted post turbo then what is the difference in temp from pre turbo? Also I've always heard that safe limit on EGTs is 1250*. I've also heard that the EGT gauges on the big riggs are post turbo. I personally set mine up post turbo since I fully intend waiting it out for just the right turbo to go with a tst box and it will need to have ball bearings. That turbo won't be cheap and I don't want its longevity to depend on whether my EGT probe comes apart and goes through the turbo. I'd much rather adjust my limit down on the gauge and have that feeling of security. Sooooo, what's the difference in pre turbo/post turbo????

 

[BRayls]

about 300 degrees cooler post mount.

 

[Dean Upson]

300* cooler has always been my understanding so 1250* post-turbo would be a little warm . There has been much discussion about probe break-up on this forum and there has been no evidence to support that theory that I have ever seen. The best arguement I've seen is that they put the probe pre-turbo on planes. The vast majority of the members here that have posted put the turbo on pre-turbo.



Dean

 

[Bertram65]

Mine is post, I see about 850 max and about 300 at shutdown. Cruising it runs anywhere from 450 to 600. I have a picture in my reader rig of where it is mounted, location would make a difference.

I have never actually heard of a probe coming apart and taking out the turbo, it looks like the way the probes are built it would almost be impossible for that to happen.

 

[Badunit]

When I had my probe post-turbo, I wasn't comfortable guessing on the pre-turbo EGT when I hit temps of 800 or higher and I wanted to be able to push it once in a while. So I moved it pre-turbo for better accuracy. My thinking is that the 300 degree rule of thumb is at a given boost and only at high EGTs. It is less than 300 degrees when cruising down the road, it is zero or negative when idling and cooling off the turbo, and it is probably less than 300 if the engine is lugging too much (low boost condition). It might be more than 300 degrees under high boost conditions (or maybe "300" has a safety factor built in). Someone with dual probes might be able to answer these questions.



I agree that the way the probe looks, it would have to degrade pretty badly before it broke off. By then you might first notice that the EGT gauge wasn't reading right.



Edit: I was flipping through a back issue of TDR (#42) and it has a short blip that says to add aproximately 10 degrees per pound of boost up to about 24-25 pounds, after that it says this "rule of thumb starts losing ground in terms of accuracy" (in other words the pre-turbo EGT gets hotter than that).

 

[David Oxland]

As far as aircraft are concerned the temps are more extreme too. 1475F naturally aspirated cruising and higher on Turbo jobs.

 

[ThomasLawrence]

I have both pre and post turbo gauges, and I've found that the 10°F/lb. does indeed hold up pretty well, in moderate driving conditions.



With that said... your thermocouple isn't going to come apart. Not gonna happen... no way, no how. These things see 1500°F or more for extended periods of time, and they don't break.



Bottom line - if you're turning up the power on your engine, you want to monitor it as accurately as possible, so you don't wind up hurting something (and that includes your $5,000 ball-bearing turbo). That mandates a pre-turbo installation.



During heavy thottle application, up hill, at speed, I can push my EGT's into the 1450°F range. My post-turbo gauge is still reading under 1000°F. Eventually, it will catch up and read close to what the formula says it should read. But, by then, damage could have occurred to the engine.



Put the pyro in the exhaust manifold where it belongs. If it makes you feel better, unscrew it once a month or so to make sure it's not about to fall off into your turbo



-Tom

 

[DocDetonancour]

I was talking to one of the "ex" cummins guys at May Maddness and he claimed that when he worked for cummins they threw bolts into the turbos as a test with no damage?????????

 

[OT-OF-HERE!!]

egts

Tks for the advice guys,. . I've changed my mind and will mount both pre and post. You convinced me. AGain, Tks.